Problem: What is the amplitude of $y=-6\sin(3\pi x+4)-2$ ?
Solution: Amplitude in sinusoids of the form $y=a\sin(bx+c)+d$ The amplitude of a sinusoid of the form $y={a}\sin(bx + c) + d$ is equal to $|{a}|$. [How can we justify this given our graphical understanding of amplitude?] Finding the amplitude The amplitude of $y = {-6}\sin(3\pi x+4)-2$ is $|{-6}|=6$.